Summary: Optical visualization to efficiently guide coronary intervention of chronic total occlusions. We propose to investigate the use of the Scanning Fiber Endoscope (SFE) during coronary intervention for chronic total occlusions of the coronary arteries (CTO). CTOs represent the most challenging angioplasties and often have much higher failure rates compared with standard angioplasty. Improved imaging of the obstructed artery has the potential to improve the success of these procedure and outcomes for the patients. The SFE is a novel endoscope design in which a single fiber is vibrated at a high speed in a spiral pattern to generate a high definition image. It much smaller in caliber compared with typical endoscopes and has been successfully used in other in vitro applications. However, it is not deliverable into the coronary arteries via typical angioplasty catheters in its current configuration. We propose in Aim 1 to modify the current SFE design to make the device more easily deliverable into the coronary arteries while minimizing changes to the imaging quality. This will incorporate a novel actuator device and a shortened fiber optic cantilever which will likely lead to better flexibility and deliverability. In addition, changes in the design of the catheter will allow for tracking along a coronary artery guide extension. In Aim 2 of our proposal will test the deliverability of the redesigned catheters in a 3 step approach. 1) An in vitro bench top model using conventional angioplasty guides and hemostatic valves will be used, with standardized criteria for successfully traversing a guide catheter and guide extension. 2) Catheter designs passing Step 1 will be tested in a perfused intact pig heart model using conventional coronary angioplasty equipment. 3) Catheters successfully used to image pig heart coronaries will be tested in a human cadaver heart perfused with expired human blood. A technique for clearing the artery of blood and imaging the artery in a standard clinical timeframe of 1 minute will be developed.